ASTROCYTES SYNTHESIZE APOLIPOPROTEIN-E AND METABOLIZE APOLIPOPROTEIN E-CONTAINING LIPOPROTEINS
ASTROCYTES SYNTHESIZE APOLIPOPROTEIN-E AND METABOLIZE APOLIPOPROTEIN E-CONTAINING LIPOPROTEINS
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DOI：
10.1016/0005-2760(87)90295-5
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发表时间：
1987-01-13
期刊：
影响因子：
--
通讯作者：
MAHLEY, RW
中科院分区：
文献类型：
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作者：
PITAS, RE;BOYLES, JK;MAHLEY, RW
我们先前已经证明星形胶质细胞原位合成和分泌载脂蛋白E。本工作采用原代培养的大鼠脑星形胶质细胞，研究载脂蛋白E的合成、分泌和代谢。培养的星形胶质细胞在高尔基体区域含有免疫反应性载脂蛋白E。星形胶质细胞与[35 S]甲硫氨酸孵育导致标记的免疫可沉淀载脂蛋白E的分泌，其占总分泌蛋白的1-3%。在培养物中分泌的载脂蛋白E和大鼠脑提取物中的载脂蛋白E与血清载脂蛋白E在两个方面不同：两者都具有略高的表观分子量（约为1000）。36，000）和比血清载脂蛋白E更多的酸性同种型。新分泌的载脂蛋白的唾液酸化解释了新分泌的载脂蛋白E和血浆载脂蛋白E的表观分子量和等电聚焦模式的差异。星形胶质细胞具有能够结合和内化含载脂蛋白E的脂蛋白的载脂蛋白B、E（LDL）受体。细胞对脂蛋白的摄取导致细胞表面受体数量的减少和胆固醇酯的细胞内积累。由于载脂蛋白E存在于脑内，并且由于脑细胞可以表达载脂蛋白B、E（LDL）受体，因此含载脂蛋白E的脂蛋白可以起到重新分配脂质和调节脑内胆固醇稳态的作用。
We have previously demonstrated that astrocytes synthesize and secrete apolipoprotein E in situ. In the present work, primary cultures of rat brain astrocytes were used to study apolipoprotein E synthesis, secretion and metabolism in vitro. The astrocytes in culture contained immunoreactive apolipoprotein E in the area of the Golgi apparatus. Incubation of the astrocytes with [35S]methionine resulted in the secretion of labeled immunoprecipitable apolipoprotein E, which constituted 1-3% of the total secreted proteins. The apolipoprotein E secreted in culture and the apolipoprotein E in rat brain extracts differed from serum apolipoprotein E in two respects: both had a slightly higher apparent molecular weight (approx. 36,000) and more acidic isoforms than serum apolipoprotein E. Sialylation of the newly secreted apolipoprotein accounted for the difference in both the apparent molecular weight and isoelectric focusing pattern of newly secreted apolipoprotein E and plasma apolipoprotein E. The astrocytes possessed apolipoprotein B,E(LDL) receptors capable of binding and internalizing apolipoprotein E-containing lipoproteins. The uptake of lipoprotein by the cells led to a reduction in the number of cell surface receptors and to the intracellular accumulation of cholesteryl esters. Since apolipoprotein E is present within the brain, and since brain cells can express apolipoprotein B,E(LDL) receptors, apolipoprotein E-containing lipoproteins may function to redistribute lipid and regulate cholesterol homeostasis within the brain.